1. Technical Field
The present invention relates to a transportation apparatus for transporting a medium, and a printing apparatus equipped with the transportation apparatus.
2. Related Art
Some printers, as an example of a printing apparatus, are equipped with a transportation apparatus that transports a print medium by using a transportation roller. In such a transportation apparatus, as the width of a medium that is to be transported increases, it is necessary to increase the length of a transportation roller in the width direction. However, a longer transportation roller makes errors in manufacturing larger, resulting in a decrease in transportation precision.
To solve these problems, in related art, the transportation roller of a transportation apparatus is formed by coupling plural driving rollers in the width direction by using Oldham coupling, for example, as disclosed in JP-A-2000-044084.
In Oldham coupling, a protrusion is formed on one of two rotary shafts that are coupled to each other, and a groove is formed in the other. A feature of Oldham coupling is that the protrusion on the one shaft slides along the groove in the other to tolerate eccentricity. Since the coupling tolerates eccentricity in this way, advantageously, allowable margin of error in the manufacturing of each driving roller increases by an amount corresponding to the eccentricity tolerance. However, in Oldham coupling, backlash increases as a result of the wear and tear of its protrusion and groove, which occurs due to repeated use because of structural reasons, resulting in a decrease in transportation precision.
The problem described above is not limited to a transportation apparatus used in a printer. The same problem arises in a transportation apparatus that includes a transportation roller for transporting a medium, and in a printing apparatus.